Default validator relative error

[Matistjati]

For context, the current output validator doesn't list the relative error, which can be frustrating:

Wrong answer on line 1 of output (corresponding to line 1 in answer file)
Too large difference.
 Judge: 155432.5000000000
 User: 155432.2666462104
 Difference: 2.333538e-01
 (abs tol 1.000000e-06 rel tol 1.000000e-06)

The relative error is "obviously" almost good enough, but too far away. Exactly how far away? I would prefer to not have to pull up a calculator to find.

Now that the code is already being touched, I propose we do the following changes:

• Also calculate and show relative error
• Add an extra space to align judge and user numbers
• Change "difference" to "Absolute error" (and have it actually be the absolute error)

Example output:

Wrong answer on line 1 of output (corresponding to line 1 in answer file)
Too large difference.
 Judge: 100
 User:  105
 Absolute error: 5.000000e+00 (abs tolerance -1.000000e+00)
 Relative error: 5.000000e-02 (rel tolerance 1.000000e-02)

I still don't think it's perfect: showing a negative tolerance is slightly confusing. However, fixing the printing for that in a non-hacky way would likely require a minor rewrite, which I feel is not worth it.